The Stack Overflow podcast is back! Listen to an interview with our new CEO.

Questions tagged [electromagnetism]

The classical theory of electric and magnetic fields, both in the static and dynamic case. Also covers general questions about magnets, electric attraction/repulsion etc. Distinct from electrical-engineering.

Filter by
Sorted by
Tagged with
0
votes
0answers
4 views

Faraday Ring: original drawing and description?

Does anyone know where this is locateed? I’ve been having a challenging time finding the original drawing with description text And experiment description. I have found a picture of the ring, ...
1
vote
3answers
3k views

Back motor effect of loaded generators?

The back motor effect (see Counter-electromotive force) is the counter torque which opposes the rotational motion of the coils in a generator when the generator is under load. The back motor effect ...
0
votes
1answer
8 views

What is responsible for large ppm shifts in HNMR analysis of paramagnetic compounds?

In H-NMR spectra of paramagnetic metal acetylacetonate compounds M(III)(acac)3, large ppm shifts are observed. This is seen with other organometallic compounds as well. What is the origin of this ...
1
vote
1answer
235 views

Magnetic flux inside solenoid

Suppose that I have a small coil that is moved at a steady rate into a solenoid. The solenoid already has a current passing through (basically, it is an electromagnet). The small coil starts beyond ...
1
vote
1answer
33 views

Symmetry Argument of a Line Charge

I am been trying to make sense of my professor's lecture notes on where he talks about line charges; in general, I am lost when it comes to the symmetry argument in the case that $E_\phi=0$ on an ...
0
votes
0answers
66 views

Why are double negative ions (Hydrogen) unstable?

This is not a duplicate. I have read these questions: Can hydrogen have 3 electrons? where Buzz says: The double hydrogen anion H−− does not exist as a stable species. (It occurs as a resonance, ...
0
votes
2answers
275 views

how is motional EMF developed?

According to my textbook and several other sources on the internet if we we move a rod in the direction perpendicular to a uniform magnetic field, the electrons will also move as per the direction ...
0
votes
1answer
30 views

“Derivation” of continuity equation

The surface integral of j over a surface S, followed by an integral over the time duration t1 to t2, gives the total amount of charge flowing through the surface in that time (t2 − t1): $${\...
0
votes
1answer
53 views

What unit system is used in Feynman's Lectures on Physics, Pt. 2

In part II, lecture 18, of Feynman's Lectures on Physics, on Table 18-1 Feynman writes Ampère's law as $$ c^2 \nabla \times \vec{B} = \frac{\vec{j}}{\epsilon_0} + \frac{\partial \vec{E}}{\partial t}. $...
0
votes
1answer
319 views

Direction of electric field between a pair of parallel plates having a positive charge in the space between them

Two parallel plates are kept in such a way that one is earthed and the other one is held at a potential $V_1$. They have a positive charge density $\rho$ in the volume between the inner faces of the ...
-1
votes
1answer
42 views

Clarification on Taylor expansion in linear quadrupole multipole expansion in cartesian coordinates

In my textbook, given the electric linear quadrupole on the z axis, as in the figure, the author considers the functions $$ \frac{1}{r_i} = \frac{1}{\sqrt{(x-x_i)^2+(y-y_i)^2+(z-z_i)^2}}, $$ with $r = ...
1
vote
1answer
25 views

Quantisation of gauge theory with minimal coupling

I have a question on the quantization of the gauge theory with minimal coupling term. What I understand is that if one is given an action $$ S=-\int d^4 x \frac{1}{4}F^2 \tag1 $$ Since this action has ...
0
votes
1answer
34 views

Could electric dipoles within hadrons provide an alternate explanation for strong force?

We all know that hadrons such as proton and neutrons are made up of quarks and not all of the quarks have the same charge. This would suggest that they have a positive and negative side. In the case ...
0
votes
1answer
31 views

Magnetic fields and electric fields relation [duplicate]

Why do we treat magnetic fields to be different from electric fields?.I thought special relativity had solved this thing.
2
votes
2answers
1k views

Work functions of ceramics/insulators

Is anyone aware of or know of a good source or means of estimating the work function of a ceramic material? Typically, work functions are given for pure elemental metals, rather than for compounds, ...
1
vote
0answers
51 views

Is Newton's third law held in special relativity regarding Coulomb's force?

Assume a charged mass $(m,+q)$ is revolved around another charged mass $(M,+q)$ at a distance $r$ so that $M>>m$, yet the gravitational effects are negligible. (Such as an electron orbiting a ...
3
votes
3answers
2k views

Can eddy currents cancel the magnetic field that causes them?

When a conductor induces eddy currents that creates a magnetic field opposing the change that created it, would the two fields at some point cancel out? Imagine the change to be so great, it induces ...
0
votes
3answers
2k views

Reflection coefficient as a function of frequency

I am trying to relate the equation for reflection coefficient in oblique mediums to the frequency but can't figure out how the frequency affects the reflection of light. $n_1$= intrinsic impedance of ...
0
votes
1answer
213 views

Can a plasma ball light up minerals that fluoresce?

I want to know if I could use a plasma ball to light up a UV poster that are typically activated by blacklights. option 1: using light from the globe According to my research it seems that the light ...
0
votes
1answer
34 views

In certain conditions, does a permanent magnet loses its mass over a period of time? [on hold]

While working on an alternative cosmological paradigm of, Eigen-rotational Clusters of String-matter Universe, it was hypothesized that the fundamental matter is, Eigen-rotational elastic string-...
1
vote
3answers
211 views

What should be the direction of motion of a conductor in a magnetic field to produce motional emf?

Here's the textbook question: Twelve wires of equal length 'l' are connected to form a skeleton cube which moves with constant velocity v perpendicular to the magnetic field B. What will be the ...
0
votes
1answer
35 views

What is a medium?

I was reading this and in there it states that The weakness of the wave theory was that light waves, like sound waves, would need a medium for transmission. The existence of the hypothetical ...
1
vote
0answers
33 views

The rate of change of a relativistic electron energy [duplicate]

I am trying to derive the equation for the rate of change of the energy for a relativistic electron. I know I should start from the following equation: $$\frac{d(\gamma m\vec{v})}{dt}=-e(\vec{E}+\vec{...
2
votes
1answer
125 views

Can one force the octupole moments of a charge distribution (neutral and with vanishing dipole moment) to vanish using a suitable translation?

In a previous question, I noted that if you have a charge distribution with nonzero charge, then it is possible to choose an origin (at the centre of charge) which makes its dipole moment vanish, and ...
-1
votes
0answers
25 views

How to calculate the refractive index of a matter consisting of chargeless particles such as neutrons?

The traditional method for deriving the index of refraction for, e.g., a gaseous medium consisting of atoms/ions, or any plasma medium, according to this note, depends on the density of electrons ...
1
vote
2answers
44 views

What causes a magnetic field to be produced at a point in space, when an electric current is flowing nearby?

We know that a current induces a magnetic field along a circular path around it But what exactly causes the magnetic field to produced in that point of space? Is it that change in the direction or ...
1
vote
1answer
173 views

How does a transformer work?

As voltage is given to primary coil, current flows through coil and consequently magnetic flux changes. Due to change in magnetic flux a back emf is also induced in the primary which opposes the ...
0
votes
3answers
4k views

Can electromagnetic fields be used to deconstruct and reconstruct atoms?

I was thinking one day and came up with a theory after reading about how scientists were studying anti-matter by using electro magnetic fields to separate matter from the anti-matter they made. It ...
1
vote
1answer
36 views

How magnetic monopole modifies faraday's law

I have encountered a statement that upon existence of magnetic monopoles, the equation $$\nabla \times \textbf{E} = -\partial_t \textbf{B}$$ must be modified. I only see that the last equation $$\...
0
votes
1answer
18 views

Does potential difference depend on the size of an object

Let's say object A has received a number x of electrons and is now at a 1v higher potential relative to a neutral ground. Now if object B which is 2 times bigger than object A receives the same ...
0
votes
2answers
55 views

Is there a connection between spontaneous symmetry breaking and massless photons?

I haven't studied a lot about these topics to put it that way. But I wonder if there is a connection between spontaneous symmetry breaking and the fact that photons are massless? The spontaneous ...
0
votes
0answers
24 views

Why are induced field lines circular?

Whenever we have a changing magnetic flux through a conductor an induced electric field is generated. It is often said that these induced electric field lines are circular in shape.But why is this so?...
0
votes
0answers
19 views

Are there experiments specifically testing for electrostatic charge when light enters a medium?

I'm aware of the Faraday effect that occurs when light enters a medium, which suggests that there could be some interactions between magnetic fields and light: https://en.wikipedia.org/wiki/...
0
votes
0answers
10 views

Forces acting on a charged particle [on hold]

List down the forces that act on a charged particle when, a) it is at rest and b) it starts to move.
0
votes
0answers
22 views

Better book for electrodynamics: Purcell or Griffiths? [on hold]

What do you think would be a better book to study electrodynamics from: Griffiths or Purcell? In terms of theory and practice.
0
votes
1answer
32 views

Does Electrostatic potential energy bend Space-time? [duplicate]

Okay, there are various questions. First, "matter and energy bends space-time" does this mean any form of energy can bend space-time? Does theory of relativity assume that there is no other form of ...
-2
votes
0answers
28 views

Magnetic field inside hollow cylinder [on hold]

A hollow thin walled conducting long cylinder of radius $R$ is carrying current I along its length. A thin slit of width $h$ is cut along the length of cylinder. What is the magnetic field just inside ...
0
votes
1answer
30 views

How does an electrical field influence a changing magnetic field?

I would like to know what happens in the following situation. (I am not planning on actually doing this - I just want to understand). Suppose I have a permanent magnet contained in a plastic capsule, ...
0
votes
1answer
10 views

Relationship between direction of magnetic force and movement of a ring

Suppose a metallic ring is dropped from above a magnet (N is pointing up and S is pointing down). Why does the "direction" of the magnetic force on the ring stay the same when it enters the ring and ...
1
vote
2answers
35 views

Why does the scattering cross section equal to the sum over all differential cross section; including the incident angle?

According to Beer Lambert's law, the intensity of light passing through a homogeneous medium diminishes at a rate proportional to the incident intensity; i.e. $$ \frac{dI(s)}{ds} = -I(s)\sigma\, , $$ ...
1
vote
1answer
6k views

Capacitance per unit area and CMOS case

In a modern 0.35 μm CMOS processor the gate oxide thickness is around 80 Å = 8 nm. This gives us a capacitance per unit area of $430~\mathrm{nF/cm^2}$ I am not getting how one gets this capacitance ...
2
votes
1answer
20 views

Why are Cauchy boundary conditions an over-specification of boundary conditions for solving Poisson’s equation?

I was referred to Physics.SE by the following content published in Jackson’s Classical Electrodynamics: This rather surprising result [the fact that the potential within a charge-free volume is ...
4
votes
2answers
1k views

In a double slit experiment, does each and every photon leave a dot on the screen in the bright area?

I have read this question: Why does the photon strike at one or another place on the tape? where PhysicsDave says: All photons passing thru the slits leave a dot on the screen, this is true for ...
0
votes
1answer
39 views

Conservation of energy when placing two inductors next to each other

Say there is a circuit with a current source and an inductor. There is a current $i(t) = at$ going through the inductor. We now place a new circuit with an inductor and a resistor next to it. The ...
0
votes
0answers
17 views

Ponderomotive Force Effect on Conductors

If I place a conductive rod of metal in an oscillating electric field, such that the ponderomotive approximation applies: $$F = \frac{q^2}{4m\omega^2}\ \text{grad} (E^2),$$ where: $q$ is charge, $m$ ...
1
vote
2answers
40 views

How should the electric field produced by an electron look like if electron is described by a wave function?

In quantum mechanics, the position of an object is not definitely known, but instead is described by a probability density function of where it would be located. Then what should the electric field ...
0
votes
0answers
10 views

Can we get energy from alternig locally the earth's magnetic field? [on hold]

Is it possible to create energy alterning between a state in which one system is under the influence of the earth's magnetic field and one in which it is isolated from it? Would it take more energy to ...
0
votes
0answers
48 views

How do I show that the two definitions of the curl of a vector field equal each other? [migrated]

The curl of a 3D vector field is a 3D vector itself and has two definitions - one in integral form and one in differential form. Definition 1: $$ \operatorname{curl}\vec{F}(x,y,z) \, \cdot \, \hat{n} ...
0
votes
0answers
10 views

What is the energy of Evanescent waves in Total Internal reflection?

In TIR, all energy is reflected back as the reflection coefficient becomes 1. Since all energy is reflected back , how come evanescent waves possess energy?
0
votes
2answers
70 views

Does a relaxing electron really accelerate?

This is not a duplicate. I am not asking about quantum leaps or quantum jumps or whether the transition is instantaneous (yes I asked that question before here Do electrons really perform ...